Imaging Assessments Flashcards
Assessing atrophy (neuronal loss)
(MRI)
Structural MRI
- Measure hippocampal volume
- Measure cortical thickness
Assessing microstructural changes
(MRI)
Conventional MRI:
- T2-FLAIR
- Postcontrast T1
Non-Conventional MRI:
- MTI, DTI, SWI
Assessing neuronal viability
(MRI)
Uses MRS
- NAA: neuronal marker
- MI: myo-inositol
Ex. Measures abnormal Glu/Gln ratio in SCA
Assessing synaptic dysfunction
(MRI/PET)
- MRS (Glu, Gln, GABA)
- PET ligand for membrane dopamine transporter (DAT)
- Single photon emission computed tomography (SPECT)
Assessing oxidative stress
(MRI)
MRS measures antioxidant activity (decreased = disease)
- GSH: glutathione
- Asc: ascorbate
Assessing impaired epigenetics
(MRI/PET)
MRS
- 31P-MRS detects high energy phosphates
- CMRglc and 13C-MRS look at the Glu-Gln cycle rate
FDG-PET
- Differentiates types of dementia (FTD, AD, DLB)
- Detects hypometabolism prior to symptoms in HD and FTD
Assessing toxic protein accumulation
(PET)
- Amyloid fibril deposition by PiB (11C) binding to AB plaques
- Intracellular tau deposition (more challenging, but NFTs correlate better with AD)
Assessing gliosis and reactive astrocytosis
(MRI/PET)
MRS
- MI (glial marker), Gln (localized in glial cells)
PET
- MAO localized in astrocytes
Assessing neuroinflammation
MRS
- BBB breakdown by DCE MRI
- Requires gadolinium-based contrast agent
- Calculates map of pharmacokinetic parameters
PET
- TSPO localized in glial cells (upregulates w/ microglial activation)
Describe the pros/cons of MRI vs. PET
MRI:
- No ionizing radiation
- Rarely uses tracers (only DCE MRI)
- Specificity depends on modality
- mM sensitivity
- 1 mm resolution
- Very available and cheap
PET:
- Ionizing radiation
- Uses tracers
- High specificity
- nM sensitivity
- 3-5 mm resolution
- Less available and expensive
